At +10 F I needed to open the pit zips on my shell after the first hill, feet and hands were fine, head and face no problem. At -10 F the body core is still fine, feet and legs are good, my fingers are getting a little cold after 30 minutes and I definitely have a cold head. Serious icing problems on the eyewear, I use contact lenses and I know from skiing that at subzero temperatures I get problems with my eyes tearing and then freezing so I need to cover them with something. Add another head layer and time to go to goggles I guess.